This invention generally relates to stackable connector assemblies and more particularly, to a stackable connector assembly which provides an interface between plug members and a printed circuit board and has a shielded signal path.
In order to conserve space on a printed circuit board, stackable connectors are employed. Stackable connectors provide a convenient way to interconnect two or more interface ports to a circuit board without consuming large amounts of space. In general, a stackable electrical connector comprises a metal bracket which supports the interface ports in a superposed relationship and a pin extension member for mating the contact elements of the interface ports with the conductors on the circuit board.
U.S. Pat. No. 5,080,609-Fabian discloses a stacked electrical connector assembly comprising a sheet metal supporting bracket having superposed upper and lower connector lugs for mounting an upper and lower interface port. The bottom surface of the bracket houses a pin header which mates directly with a printed circuit board. The upper interface is connected to the pin header by a flat cable which extends downwardly from the top of the upper interface. The lower interface is in contact with the circuit board via bent contact tails which extend from the rear of the lower interface through the bottom of the bracket.
Connectors of the type disclosed in Fabian must be secured onto the printed circuit board. Normally, this is accomplished when the pin contacts of the connector are mated with corresponding receiving ports on the circuit board. The mechanical link between the pins and the ports is augmented by screws placed through openings located at the bottom of the central support bracket which correspond to openings on the circuit board. Before the screws are placed through the openings on the connector and circuit board, the connector""s pin contacts are mated onto the circuit board. A drawback to this system is that once the pin contacts of the connector are mated into the circuit board, inserting screws can cause lateral movement of the connector which could result in damage to the pin contacts.
Stacked connectors must also provide for shielding from electromagnetic emissions. Electromagnetic emissions induce currents that adversely affect the transmission of electric signals. In a typical stacked connector, such as the one disclosed in Fabian, a signal received through one interface can induce a current in an adjacent interface. Often, the wiring set between the upper interface and the circuit board and the wiring set between lower interface and the circuit board, are positioned in close proximity to each other. This close proximity increases the likelihood that a signal received by an interface and communicated to the printed circuit board will either interfere with, or generate a false signal in, the adjacent interface.
In order to prevent stray currents, stacked electrical connectors have been provided with shielding. For example, U.S. Pat. No. 5,085,590-Galloway, discloses an electrical connector similar to Fabian with the addition of a metallic shield member which is placed between, and parallel to, the upper and lower interfaces. The shield member is intended to block electromagnetic emissions from the two interfaces from reaching each other. However, the shield is insufficient since it does not extend along the entire length of the connector. This can allow substantial electromagnetic emissions from the interfaces to travel around the ends of the shield.
Currently, there is no stacked connector available which can be easily, but sufficiently, latched to a printed circuit board and which stacked connector also provides complete shielding from electromagnetic emissions. Thus, a need exists for such a stacked connector.
According to the present invention, a stacked electrical connector is provided which is mounted onto a primary circuit board for providing a stacked interface for multiple plug elements. The connector is easily and securely mounted to the circuit board and prevents the formation of stray currents along the signal path of the connector.
The stacked connector generally comprises a frame which defines a first and a second interface. The interfaces are spaced in substantially parallel and vertical juxtaposition to each other along the length of a frame and are electrically coupled to a primary circuit board. Each interface mates with a plug member whereby the interfaces are also electrically coupled to the primary circuit board. The interfaces are defined within and completely enclosed by the frame. The frame is constructed so that when the plug elements are placed within the interfaces, they are securely retained therein in isolation from each other. In particular, the interfaces include side walls, an inner wall and an outer wall. Each interface is located within the frame so that its inner walls face each other. The inner walls are constructed from a conductive material such that they shield the end of the plug members from electromagnetic emissions.
The plugs are maintained within the interfaces by an interference fit. In order to increase the interference fit, each plug member is provided with a latch. The outer wall of each interface includes a latching notch and a surface which engages the latch of the plug elements. The latching notch acts as a guide for the latches, and hence the plug members, as they are inserted into the interfaces. As the latches are inserted into the interfaces, they engage the inner surfaces of the outer walls increasing the interference fit between the plug and the interface.
Each interface is electrically coupled to the primary circuit board by an intermediate circuit board. The intermediate circuit board is mounted on the frame perpendicular to the interfaces. Each interface includes contacts which at one end define receptacle sections and at the opposite end define pin contacts. The pin contacts mate with contact slots on the intermediate circuit board which is directly coupled to the primary circuit board. Alternatively, the pin contacts of the interfaces are connected directly to the primary circuit board by a flat wire or multiple independent wires.
The pin contacts of each interface extend beyond the inner wall of the interfaces, into the circuit board. Thus, the inner walls do not shield the pin contacts of the interfaces from each other. In order to shield the pin contacts from each other, a shielding circuit board is mounted to the intermediate circuit board so as to extend within the frame between and parallel to the interfaces. The shielding circuit board extends along the entire width of the frame so as to abut the walls of the frame and completely isolate the pin contacts from each other.
The intermediate circuit board is electrically coupled to the primary circuit board by a right angle header. The right angle header includes pin contacts which mate with contact slots on the primary circuit board. The mechanical link between the contact pins and the slots retain the connector on the primary circuit board. Often, the mechanical link between the header pins and the circuit board is insufficient to retain the connector onto the primary circuit board. Additional mechanical support between the connector and primary circuit board is provided by at least two flexible retention studs mounted onto the bottom of the frame. Each of the retention studs have inwardly tapered edges so that their distal ends are wider than their proximal ends. The studs mate with corresponding retention slots on the primary circuit board. As the studs are placed into the slots, they are compressed inwardly. Once through the slots, the distal ends of the studs expand pressing the circuit board in contact with the bottom of the connector.